1. Field of the Invention
The present invention relates to a device for bending a wire to be used in the fabrication of a removable orthodontic appliance. More particularly, the device is for use in fabricating a retainer of the type having a wire against the labial surface of the upper or lower anterior teeth.
2. Brief Description of the Prior Art
At the present time, the procedure for making a removable orthodontic appliance is as follows. First, an impression of the teeth is made, from which is molded a plaster model of the patient's teeth. Wires are then shaped and adapted to the model and an acrylic plate is formed over the tag ends of the wires.
A labial bow is an important element in a Hawley retainer and is used in many other orthodontic appliances. When the retainer includes a labial bow, a length of wire is cut and a pair of vertical loops are formed in the canine areas separated by an incisor segment. The vertical loops ideally consist of parallel legs joined by a smooth curve. The loops are symmetrical and extend a short distance above the gingival margin. Either before the vertical loops are formed or after, the incisor segment is curved such that it passes across the labial surface of the incisors at the widest portion of the teeth just incisal to the interdental papilla. The wire should form a smooth arc, as symmetrical as possible while conforming to the curve of the labial surfaces of the incisors. Special pliers such as 139 pliers are used to form the vertical loops and a turret may be found helpful in shaping the incisor segment.
Making a proper labial bow requires skill and it is desirable to keep time to a minimum. Quality is improved if repeated bending is eliminated because repeated bending of the wire can lead to strain hardening and weakening in certain metals. Quality is also improved if handling of the wire by wire forceps is kept to a minimum as damage to the wire may lead to increased likelihood of breakage.